Hurricane Hector regained strength in the eastern Pacific late on Sunday and swelled into a Category 4 storm again with sustained 140 mph winds as it stayed on target to possibly hit Hawaii by midweek, officials said.
Some predictions put the storm on a virtual collision course with the Kilauea Volcano on the southern part of the island. Lava has been spewing from vents on its eastern flank since May 3 and its summit crater is collapsing.
The National Hurricane Center put Hector about 1,130 miles southeast of Hawaii's Big Island and its hurricane force winds stretched 30 miles out from its center with tropical force winds of 74 mph extending out 105 miles, the NHC said.
It was expected to pick up speed from its 14 mph westward crawl into the central Pacific on Monday, the center said in an advisory late on Sunday.
The NHC forecast gradual weakening on Monday night through to Wednesday.
It was uncertain if it would hit or just brush by the southern edge of the Big Island, said a meteorologist at the National Weather Service's Weather Prediction Center in College Park Maryland.
Scientists differ over how hurricanes and volcanoes might interact, including the question of whether low atmospheric pressure could help trigger an eruption.
Two tropical storms formed in the Pacific Ocean off southwestern Mexico, but neither posed any immediate threat to land as they took tracks predicted to move parallel to the coast.
The U.S. National Hurricane Center said Tropical Storm John was expected to strengthen rapidly and become a hurricane by Monday night or Tuesday. Tropical Storm Ileana was trailing John to the southeast but wasn't forecast to reach hurricane force.
Farther out to sea, a strengthening Hurricane Hector headed for the central Pacific as a Category 4 storm, with winds of 140 mph (220 kph), the hurricane centre reported. It was centred about 1,130 miles (1,820 kilometres) east-southeast of South Point, Hawaii, and was moving west at 14 mph (22 kph).
—The Associated Press contributed to this report.